The present disclosure relates to an image forming apparatus provided with a staple unit.
Some image forming apparatuses are fitted with a post-processing device (finisher). Post-processing devices perform various kinds of post-processing on printed sheets. For example, post-processing devices include a punch mechanism and a staple mechanism. The punch mechanism creates holes in printed sheets. The staple mechanism staples a bundle of sheets. When an image forming apparatus makes a transition to a power saving state, a post-processing device may also be brought into a power saving state. In this case, supply of electric power to the post-processing device stops. Thus, even when the post-processing device is used (contrary to the user's intention), supply of electric power to the post-processing device may stop.
One example of a technology is known for preventing a post-processing device, while in use, from being brought into a power saving state. Specifically, there is known an image forming apparatus connected to a finisher, wherein supply of electric power is controlled such that the image forming apparatus is either in a power saving state or in a non-power saving state, a transition to a power saving state is prohibited when sheets are detected having been set in the finisher, and a transition to a power saving state is made when no sheets are detected being set in the finisher on condition that a condition to make a transition to a power saving state is met.
Electric power is supplied to an optionally fitted unit such as a finisher usually from the main body (printer portion) of the image forming apparatus. Thus, when the main body of the image forming apparatus is brought into a power saving state, supply of electric power to the unit stops. This also brings the unit into a power saving state.
In the above-described known technology, sheets having been set in the finisher are detected. While sheets are being set in the finisher, the image forming apparatus recognizes that the user is operating the finisher. In the above-described known technology, for example, a CPU controls the transition to a power saving state. The above-described known technology presupposes recognizing that whether or not the finisher is mounted and recognizing whether or not sheets have been set in the finisher. That is, it presupposes that the control circuit in the main body and the finisher are communicably connected together via a plurality of signal lines.
On the other hand, some units fitted to image forming apparatuses are supplied only with electric power from the image forming apparatuses. Focusing exclusively on supply of electric power advantageously helps achieve simple wiring, reduced development man-hours, and reduced manufacturing cost. In this case, the control circuit in the main body and the fitted unit are not connected via a communication signal line. No data communication is performed between the control circuit and the fitted unit. The control circuit cannot check the condition of the fitted unit. For example, the control circuit cannot check whether or not the fitted unit is connected or whether or not sheets have been set in it.
It is necessary to bring also the fitted unit into a power saving state. Usually, when the image forming apparatus makes a transition to a power saving state, supply of electric power to the fitted unit whose condition cannot be checked stops. It can occur that, to effect the transition to a power saving state, supply of electric power to the fitted unit inconveniently stops when the user is about to use the fitted unit which does not communicate with the control circuit. When the supply of electric power stops, the fitted unit cannot be used.
Thus, the above-described known technology is not applicable to an image forming apparatus in which no communication is performed between a control circuit in its main body and a fitted unit. The above-described known technology cannot deal with the above-discussed problem.